Jasmine's was a difficult pregnancy. She was completely bedridden with Theodore, then recovered slowly after his birth. Theodore was born on 1 July in the Imperial City of Luthien. Because Jasmine knew she could never conceive again, she lavished love of her only child in a decidedly un-Kuritan fashion, though the coldness of Takashi balanced this out.

It was with the Legions of Vega that Theodore began his programs for reform. He saw the problems with the military doctrine of the Draconis Combine, notably their insistence on attacking the center of their enemies' line and the enacting of the rite of seppuku by otherwise good commanders. [6] Thanks to his leadership, the Combine was able to fight off the Lyran Commonwealth's invasion of Vega during the Fourth Succession War. Later, Theodore exploited the machinations of Duke Aldo Lestrade of Skye and led a counterattack on several undefended Lyran worlds near the regional capital of Skye, threatening the important world. This action forced Archon Katrina Steiner to use her reserve forces, including the 10th Lyran Guards and the 1st Royal Guards to counter-assault the Kuritan juggernaut.

After the 4th War, Theodore's military acumen had become widely known, so his father was almost forced to promote him to the rank of Gunji-no-Kanrei (Deputy for Military Affairs) in 3031. Takashi planned on reining Theodore in, but Theodore jumped at the opportunity to push his new interpretation of bushido, which he began with the Genyosha and Ryuken. Perhaps his most brilliant move as Kanrei was agreeing to recognize the independence of the Free Rasalhague Republic. In doing so, he bilked the Lyrans out of all of the gains from the 4th War and received aid from ComStar in the form of new, high-tech BattleMechs. These 'Mechs came in handy when the Federated Commonwealth launched its invasion in 3039.

The War of 3039 was a brief affair. After Prince Hanse Davion launched his invasion, Theodore mustered the forces for a counterattack, which captured the factory world of Quentin. Hanse stopped the assault in the face of the Combine's apparent strength. It was not until more than ten years later that he learned Theodore's counterattack had been a bluff, and that he had banked the survival of the Combine on Hanse backing down.

The 3040s were peaceful, but 3050 brought news of a strange invader from the Periphery. When the Clans appeared, it fell to Theodore to organize the nation's defenses against what seemed at times to be an unstoppable threat. On Wolcott, he was able to trap the Smoke Jaguars, a plan executed by his son Hohiro and Shin Yodama. The Combine was then able to obtain four fully operational OmniMechs, two dozen ElementalBattle Armor infantry suits, and considerable salvage from the defeated Jaguars. Perhaps most importantly, the Jaguars were forbidden from attacking the planet ever again.

Later, Theodore traveled with the other leaders of the Inner Sphere to Outreach in 3051 for the purposes of a summit aimed at defeating the Clans. There, Jaime Wolf provided information to Theodore and the others, while he and Hanse agreed on a truce with the threat of a superior enemy. In 3052, Clans Smoke Jaguar and Nova Cat launched a joint invasion of Luthien. Hanse sent both the Kell Hounds and Wolf's Dragoons to aid the DCMS forces, which included units that followed both Theodore's reforms and the old ways that Takashi espoused. The victory by these disparate elements helped reconcile father and son, though successful brain surgery on Takashi also helped his mental state. Ironically, the Clan Invasion helped Theodore's cause by giving so many traditionalist samurai the glorious death in battle that many of them so wanted.

Though father and son would find some measure of respect for one another after these events, life in the Imperial Court remained uneasy at times. Then suddenly in 3054, Theodore's long power struggle with his father ended with Coordinator Takashi's seppuku.

As Coordinator, Theodore vowed to focus on the Clans and stay out of petty Inner Sphere political squabbles. He instituted the Phoenix Programs, which were targeted at rebuilding the DCMS. To do this, he directed them to recruit heavily from non-traditional sources such as women and yakuza. He also allowed ComStar to stage Explorer Corps missions from DCMS bases, both within the Combine and the Deep Periphery, ostensibly with the goal of finding the Clan territories. Domestically, he initiated the Environmental Reclamation Program, a portion of which transplanted over 5,000 acres of trees to the vicinity of the Buda Weapons Sector on the Luthien continent of Aichi.[7]

Theodore could not keep his Combine out of the way forever, and sent in peacekeepers under ComStar's aegis into the Chaos March shortly after its creation, mostly in the Lyons Thumb. Reactionary conservative elements within the Combine did not think this was enough, however, and invaded the world of Towne in 3058. Though they were stopped by the mercenary unitCamacho's Caballeros, they then tried to assassinate Theodore at his birthday celebration in that year. The kokuryu-kai were again stopped by the Caballeros.

3058 also saw the resurrection of the Star League and its goal of annihilating a Clan. Theodore successfully argued for that Clan to be Clan Smoke Jaguar, the most repressive of the Clans towards their conquered peoples. Though DCMS forces made up the bulk of the Star League troops, the Combine benefited greatly from the Inner Sphere coalition that aided them. Theodore worked on reintegrating the liberated worlds into the Combine, while other leaders went after the Jaguar capital on Huntress.

Theodore was accused of abusing his power as First Lord when he annexed the Lyons Thumb in 3062. In that year, the kokuryu-kai showed themselves once more when they hired mercenary units to attack Lyran troops under DCMS colors. Similarly, "Lyran" troops attacked DCMS garrisons. When a real Lyran unit counterattacked, Theodore seized the Lyons Thumb to "ensure the stability of the region."[citation needed]

In 3062, forces from Clan Ghost Bear and the Federated Commonwealth's Draconis March attacked the Combine. The Bears did so because of a misjudged assault on their new capital of Alshain by the kokuryu-kai-influenced Alshain Avengers, while the March did so because of a perceived weakness borne out of distraction. Theodore received unsolicited aid in the form of Clan Hell's Horses, which attacked the Bears from the other flank, causing the Ghost Bears to sue for peace. With one border secured thanks to the Trial of Courchevel, Theodore sent his troops to beat back the nominally-FedCom invaders and conquered two planets for the trouble.

While trying to direct the DCMS from Dieron and plan a campaign to liberate Luthien, Theodore suffered a stroke that rendered him comatose,[9] and which finally killed him in 3070. His reforms of the DCMS would later have to be scaled back by Hohiro to appease the hard-liners that still existed within the military.

From the ashes of political divisiveness, Terra rose once more like a proud phoenix. If the analogy holds true, Terra may one day rise again in political importance, capable of casting her shadow over House Kurita and the Draconis Combine. This is something we must not let happen, even if we are forced to attack Terra directly!